155. Minimum Depth of Binary Tree

155. Minimum Depth of Binary Tree

Description

Given a binary tree, find its minimum depth.
The minimum depth is the number of nodes along the shortest 
path from the root node down to the nearest leaf node.

Example

Given a binary tree as follow:
  1
 / \ 
2   3
   / \
  4   5

Solution

/**
 * Definition of TreeNode:
 * public class TreeNode {
 *     public int val;
 *     public TreeNode left, right;
 *     public TreeNode(int val) {
 *         this.val = val;
 *         this.left = this.right = null;
 *     }
 * }
 */

public class Solution {
    /**
     * @param root: The root of binary tree
     * @return: An integer
     */
    public int minDepth(TreeNode root) {
        // write your code here
        if(root!=null){
            int mindl = minDepth(root.left);
            int mindr = minDepth(root.right);
            int mind = 0;
            //注意這裏，和求最大深度不一樣，如果左右子樹有一棵爲空，那麼此時深度爲非空的那棵子樹的深度
            if(mindl==0||mindr==0) mind = mindl==0?mindr:mindl;
            else{
                mind = mindl>mindr?mindr:mindl;
            }
            return mind+1;
        }else{
            return 0;
        }
    }
}